scholarly journals Co-Seismic and Post-Seismic Temporal and Spatial Gravity Changes of the 2010 Mw 8.8 Maule Chile Earthquake Observed by GRACE and GRACE Follow-on

2020 ◽  
Vol 12 (17) ◽  
pp. 2768
Author(s):  
Wei Qu ◽  
Yaxi Han ◽  
Zhong Lu ◽  
Dongdong An ◽  
Qin Zhang ◽  
...  
Keyword(s):  
Gravitational Field ◽  
Hanging Wall ◽  
Suppressive Effect ◽  
Gravity Gradient ◽  
Dislocation Model ◽  
Seismogenic Fault ◽  
First Order ◽  
Gravity Changes ◽  
Maule Earthquake ◽  
Temporal And Spatial

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (GRACE-FO) satellites are important for studying regional gravitational field changes caused by strong earthquakes. In this study, we chose Chile, one of Earth’s most active seismic zones to explore the co-seismic and post-seismic gravitational field changes of the 2010 Mw 8.8 Maule earthquake based on longer-term GRACE and the newest GRACE-FO data. We calculated the first-order co-seismic gravity gradient changes (GGCs) and probed the geodynamic characteristics of the earthquake. The earthquake caused significant positive gravity change on the footwall and negative gravity changes on the hanging wall of the seismogenic fault. The time series of gravity changes at typical points all clearly revealed an abrupt change caused by the earthquake. The first-order northern co-seismic GGCs had a strong suppressive effect on the north-south strip error. GRACE-FO results showed that the latest post-seismic gravity changes had obvious inherited development characteristics, and that the west coast of Chile maybe still affected by the post-seismic effect. The cumulative gravity changes simulated based on viscoelastic dislocation model is approximately consistent with the longer-term GRACE and the newest GRACE-FO observations. Our results provide important reference for understanding temporal and spatial gravity variations associated with the co-seismic and post-seismic processes of the 2010 Maule earthquake.

MULTI-SCALE MECHANICAL BEHAVIOR ANALYSIS ON FLUID–SOLID COUPLING FOR OSTEONS IN VARIOUS GRAVITATIONAL FIELDS

2021 ◽  
Author(s):  
HAO ZHANG ◽  
HAI-YING LIU ◽  
CHUN-QIU ZHANG ◽  
ZHEN-ZHONG LIU ◽  
WEI WANG
Keyword(s):  
Gravitational Field ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Gravity Gradient ◽  
Static Compression ◽  
Gravitational Fields ◽  
Multi Scale ◽  
Earth’S Gravitational Field ◽  
Mechanical Microenvironment

Background: Compact bone mainly consists of cylindrical osteon structures. In microgravity, the change in the mechanical microenvironment of osteocytes might be the root cause of astronauts’ bone loss during space flights. Methods: A multi-scale three-dimensional (3D) fluid–solid coupling finite element model of osteons with a two-stage pore structure was developed using COMSOL software based on the natural structure of osteocytes. Gradients in gravitational fields of [Formula: see text]1, 0, 1, 2.5, and 3.7[Formula: see text]g were used to investigate the changes in the mechanical microenvironment on osteocyte structure. The difference in arteriole pulsating pressure and static compression stress caused by each gravity gradient was investigated. Results: The mechanical response of osteocytes increased with the value of g, compared with the Earth’s gravitational field. For instance, the fluid pressure of osteocytes and the von Mises stress of bone matrix near lacunae decreased by 31.3% and 99.9%, respectively, in microgravity. Under static loading, only about 16.7% of osteocytes in microgravity and 58.3% of osteocytes in the Earth’s gravitational field could reach the fluid shear stress threshold of biological reactions in cell culture experiments. Compared with the Earth’s gravitational field, the pressure gradient inside osteocytes severely decreased in microgravity. Conclusion: The mechanical microenvironment of osteocytes in microgravity might cause significant changes in the mechanical microenvironment of osteocytes, which may lead to disuse osteoporosis in astronauts.

Speed and accuracy improvements in standard algorithm for prismatic gravitational field

2020 ◽  
Vol 222 (3) ◽  
pp. 1898-1908
Author(s):  
Toshio Fukushima
Keyword(s):  
Gravitational Field ◽  
Exact Formula ◽  
New Method ◽  
Gravity Gradient ◽  
Gradient Tensor ◽  
Gravity Gradient Tensor ◽  
Triple Difference ◽  
Transcendental Functions ◽  
Arctangent Function ◽  
Speed And Accuracy

SUMMARY By utilizing the addition theorems of the arctangent function and the logarithm, we developed a new expression of Bessel’s exact formula to compute the prismatic gravitational field using the triple difference of certain analytic functions. The use of the new expression is fast since the number of transcendental functions required is significantly reduced. The numerical experiments show that, in computing the gravitational potential, the gravity vector, and the gravity gradient tensor of a uniform rectangular parallelepiped, the new method runs 2.3, 2.3 and 3.7 times faster than Bessel’s method, respectively. Also, the new method achieves a slight increase in the computing precision. Therefore, the new method can be used in place of Bessel’s method in any situation. The same approach is applicable to the geomagnetic field computation.

scholarly journals A relativistic orbit model for the LISA mission to be used in LISA TDI simulators

2009 ◽  
Vol 5 (S261) ◽  
pp. 124-129
Author(s):  
Sophie Pireaux ◽  
Bertrand Chauvineau
Keyword(s):  
Gravitational Field ◽  
Time Delay ◽  
Gravitational Waves ◽  
Frequency Band ◽  
The Novel ◽  
Keplerian Orbit ◽  
First Order ◽  
Interferometry Method ◽  
Orbit Model

AbstractThe LISA mission is an interferometer, formed by three spacecraft, that aims at the detection of gravitational waves in the [10−4, 10−1] Hz frequency band. Present LISA TDI simulators, aimed at validating the novel Time Delay Interferometry method, use a classical Keplerian orbit model at first order in eccentricity in the gravitational field of a spherical non-rotating Sun, without planets. We propose to use the same model but described in the framework of relativistic gravity, and we focus here on quantifying the differences between classical and relativistic orbits for the LISA spacecraft, under the same assumptions.

scholarly journals Coseismic Deformation and Speculative Seismogenic Fault of the 2017 MS 6.6 Jinghe Earthquake, China, Derived From Sentinel-1 Data

2021 ◽  
Vol 9 ◽  
Author(s):  
Wei Feng ◽  
Zechao Bai ◽  
Jinwei Ren ◽  
Shuaitang Huang ◽  
Lin Zhu
Keyword(s):  
European Space Agency ◽  
Image Data ◽  
Junggar Basin ◽  
Deformation Field ◽  
Slip Distribution ◽  
Coseismic Deformation ◽  
Dislocation Model ◽  
Seismogenic Fault ◽  
Geological Investigation ◽  
Maximum Deformation

A MS 6.6 earthquake struck Jinghe County in Bortala Mongol Autonomous Prefecture of Xinjiang Uygur Autonomous Region on August 9, 2017. The earthquake occurred near the eastern part of the Kusongmuxieke Piedmont Fault (KPF) in the southwest of Junggar Basin. Using two pairs of coseismic SAR image data from the ascending and descending tracks from Sentinel-1 (European Space Agency), we processed the interferograms to obtain the coseismic deformation field. We calculate the fault slip distribution of the earthquake based on the elastic half-space rectangular dislocation model with the available location, geometry from seismic data and the coseismic deformation data. The results show that the earthquake deformation field has the typical characteristics of thrust faulting. The uplift deformation field is about 28 km long and 20 km wide. The maximum displacements of InSAR line-of-sight to the ascending and descending tracks are 49 and 68 mm, respectively. The main slip is concentrated at the depth of 10–20 km. The inverted seismic moment is equivalent to a moment magnitude MW 6.3. This result is very similar to the slip distribution from the seismological inversion. The maximum deformation area and the distribution of aftershocks are both on the west side of the mainshock. They mutually confirm the characteristics of a unilateral rupture. According to stress triggering theory, the aftershocks within 1 month after the mainshock in the layer 10–14 km deep may have been triggered by the mainshock, and the transferred stress increases the seismic risk of the eastern section of the KPF fault. After more than 1 year, a MS 5.4 earthquake occurred to the southwest of the MS 6.6 Jinghe earthquake. Beacause the stress drop change (<0.01 MPa) is too small for the MS 5.4 earthquake to have been directly triggered. Based on the analysis of multisource data and the detailed geological investigation, the thrust Jinghenan fault which north of Kusongmuxieke Piedmont fault is inferred to be the seismogenic fault of the MS 6.6 Jinghe earthquake.

Proof that Einstein’s field equations are invalid: Exposition of the unimodular defect

2021 ◽  
Vol 34 (4) ◽  
pp. 420-428
Author(s):  
Stephen J. Crothers
Keyword(s):  
Gravitational Field ◽  
Differential Invariant ◽  
Albert Einstein ◽  
Mathematical Foundation ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Field Equations ◽  
First Order ◽  
Gravitational Field Equations ◽  
Pure Mathematics

Albert Einstein first presented his gravitational field equations in unimodular coordinates. In these coordinates, the field equations can be written explicitly in terms of the Einstein pseudotensor for the energy-momentum of the gravitational field. Since this pseudotensor produces, by contraction, a first-order intrinsic differential invariant, it violates the laws of pure mathematics. This is sufficient to prove that Einstein’s unimodular field equations are invalid. Since the unimodular form must hold in the general theory of relativity, it follows that the latter is also physically and mathematically unsound, lacking a proper mathematical foundation.

scholarly journals A possible precursor prior to the Lushan earthquake from GPS observations in the southern Longmenshan

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Qixin Wang ◽  
Xiwei Xu ◽  
Zaisen Jiang ◽  
John Suppe
Keyword(s):  
Wenchuan Earthquake ◽  
Epicentral Distance ◽  
Elastic Strain Energy ◽  
Lushan Earthquake ◽  
Dislocation Model ◽  
Seismogenic Fault ◽  
2008 Wenchuan Earthquake ◽  
The 2008 Wenchuan Earthquake ◽  
Longmenshan Thrust Belt ◽  
Preseismic Deformation

AbstractGlobal Positioning System (GPS) stations installed in and around the epicenter of the Lushan earthquake (Mw 6.7), which occurred almost 5 years after the 2008 Wenchuan earthquake, recorded preseismic deformation corresponding to the Lushan earthquake within the southern Longmenshan thrust belt. A half-space dislocation model is used to simulate the theoretical values of the postseismic displacements caused by the 2008 Wenchuan earthquake, and after transforming the reference frame and filtering the GPS displacement time series, the theoretical and observed GPS values are compared to identify the geodetic anomaly preceding the Lushan earthquake. The abnormal extent of this geodetic anomaly decreases with increasing epicentral distance for each GPS site. This geodetic signal reflects preslip along a locked section of the 2013 seismogenic fault, which caused the accumulation of elastic strain energy until the faulting strength was overcome, thereby generating the Lushan earthquake. Hence, this anomaly might be used as an observable and identifiable precursor to forecast an impending earthquake within a period of less than two and half years before its occurrence.

scholarly journals Semiclassical bosonic D-brane boundary states in curved spacetime

Open Physics ◽  
2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Ion Vancea
Keyword(s):  
Gravitational Field ◽  
Center Of Mass ◽  
Quantization Method ◽  
Strong Gravitational Field ◽  
First Order ◽  
Boundary States ◽  
Spacetime Metric ◽  
Algebraic Constraints ◽  
Semiclassical State ◽  
First Order Perturbation

AbstractIn this paper we discuss the existence of quantum D-brane states in the strong gravitational field and in the presence of a constant Kalb-Ramond field. A semiclassical string quantization method in which the spacetime metric g AB and the constant antisymmetric Kalb-Ramond field b AB are treated exactly is employed. In this framework, the semiclassical D-branes are defined at the first order perturbation around the trajectory of the center-of-mass of a string. The set of equations the semiclassical D-branes must satisfy in a general strong gravitational field are given. These equations are solved in the AdS background where it is shown that a D-brane coherent state exists if the operators that project the string fields onto the corresponding Neumann and Dirichlet directions satisfy a set of algebraic constraints. A second set of equations that should be satisfied by the projectors in order that the semiclassical state be compatible with the global structure of the D-brane are derived in the particle limit of a string in the torsionless AdS background.

scholarly journals First-Order Leveling Reveals Anomalous, Interseismic, Contractile, Transient Strain Across Teton Normal Fault, 1988-2001, Grand Teton National Park, Wyoming

2001 ◽  
Vol 25 ◽  
pp. 104-110
Author(s):  
A. Sylvester ◽  
R. Smith ◽  
Wu Chang ◽  
C. Hitchcock
Keyword(s):  
Hanging Wall ◽  
Normal Fault ◽  
Seismic Gap ◽  
Crustal Shortening ◽  
First Order ◽  
Gps Survey ◽  
Jackson Hole ◽  
Subsidence Zone ◽  
Teton Range ◽  
Yellowstone Caldera

As part of a comprehensive neotectonic study of interseismic behavior of active faults, we have done six first order leveling surveys of 50 permanent bench marks in a 22 km-long base line across the Teton fault to characterize its interseisrnic behavior between 1988 and 2001. This 55 km-long normal fault extends along the eastern base of the Teton Range, exhibits up to 30 m of post-glacial offset, and has one the highest rates of Holocene slip of any fault in the Basin-Range. It is seismically dormant at the M2+ level, however, and presently lies in the center of a 50 km-long seismic gap. Results of five of the six levelings are remarkably similar and suggest that the alluvium-filled valley of northern Jackson Hole (hanging wall) subsided 6-8 mm relative to bedrock of the Teton Range (footwall) relative to the 1989 survey. Height changes were insignificant from 1989 to 1993. In 1997, however, a 2 km-wide zone adjacent to the fault rose 12 mm relative to the 1993 survey, and then dropped 16 mm by the 2001 leveling. This zone coincides with an area of low topography characterized by lakes ponded along the fault and south-flowing streams parallel to the range front, rather than eastward away from the range. This subsidence zone records hanging wall subsidence related to long term faulting. The 1997 uplift of the valley floor and subsidence zone may reflect an unexpected, reverse loading and local crustal shortening between 1993 and 2001. Campaign GPS surveys (1987 to 2000, only briefly summarized in this report) support this hypothesis, indicating that the principal direction of horizontal shortening was locally E-W perpendicular to the fault, and that crustal shortening occurred in the period 1995-2000. Regionally during 1987-1995, subsidence and shortening characterized deformation of the Yellowstone caldera when GPS recorded uplift and extension across the Teton fault, only 30 km to the south. During 1995-2000, subsidence slowed or ceased for much of the caldera, whereas the overall GPS vectors across Jackson Hole were directed west with almost 2 mm/yr of E-W motion (N. America fixed). This shortening strain field implies that the regional stress field was compressional normal to the fault at the time of the 2000 GPS survey. The return of the 2001 leveling signal to pre-1997 values suggests that the strain reversed or relaxed, and that the 1997 leveling anomaly was a contractile strain transient that passed across the fault probably between 1995, when the strain pattern at Yellowstone caldera changed, and the 2000 GPS survey but before the 2001 leveling. Preliminary elastic dislocation models indicate 10-20 mm reverse slip at a depth of 1-2 km. Alternatively the observed leveling changes may reflect a complex combination of other processes including local poroelastic effects, or nearfield drag of the hanging wall as it subsides overall in farfield extension.

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